Just these already offer a huge palette. I have some extra stuff around like a Kyma system and stuff, but use them less often (maybe I should steer my focus).

But I cannot pinpoint a single synth that's "best", because they all offer different workflows and are better suited for different sound categories.

From what I have I would probably say Absynth 5 to be the best synth I currently own. Obviously it doesn't do all the things like e.g. the Kyma, but it gets more use than the Kyma right now, so that's why I think it's the best synth out of what I have

I was going to say that I liked Parsec's demo but that I found the thing expensive, but I went to check online and it's on sale for $60! I was using Dexed so far, but I might jump the gun and get Parsec with that discount.